Microsoft warned customers about computer code that exploits holes in the company's software and blamed security researchers for publishing proof of concept code to trigger the vulnerabilities, which was then turned into working attacks.

The company issued a statement on its Web site last Thursday citing an increased risk to users of its Windows operating system MSN Messenger instant messenger (IM) application and Office XP software suite. Microsoft singled out Finjan Software and Core Security Technologies for publishing code to test for the vulnerabilities shortly after software patches were released to plug the holes.

Finjan released code to test for a hole its researchers discovered in Microsoft Office XP, and that Microsoft fixed with a patch described in Security Bulletin MS05-005. Finjan, a San Jose, California, maker of content management technology, discovered and then publicized code to test for the vulnerability on the same day Microsoft released its bulletin, Microsoft said.

The buffer overflow in question affects a process that passes Web URL (Uniform Resource Locator) information to Office XP applications and could be used by malicious hackers to hide attacks in HTML (Hypertext Markup Language) links embedded in e-mail messages or Web pages. (See: http://www.microsoft.com/technet/security/bulletin/MS05-005.mspx.)

Microsoft also criticized Core Security Technologies of Boston for publishing a proof of concept for a hole in an MSN Messenger component called "libpng," which is used to display PNG (Portable Network Graphics) files. On Tuesday, Microsoft released a patch, MS05-009, that fixed several holes in libpng for the PNG hole and labeled the vulnerability "critical." (See: http://www.microsoft.com/technet/security/bulletin/MS05-009.mspx.) An exploit based on that proof of concept was posted on the Internet shortly thereafter, Microsoft said.

The actions by Finjan and Core could allow malicious hackers to launch attacks on Microsoft customers who have not had time to install patches for the affected software, said Stephen Toulouse, program manager at Microsoft's Security Response Center.

"We're concerned that hackers will take this information and use it. Once you have code that describes how to get from A to B to C, it's not hard to get to Z if that's your goal," he said.

Toulouse cited the SQL Slammer worm, which targeted Microsoft's SQL Server database as an example of proof of concept code that was modified to create a virulent Internet worm.

Microsoft encourages security researchers to wait before publishing the code, Toulouse said, adding that 90 days is an accepted standard within the security research community to delay publication of proof of concept code.

An executive at Core Security denied that the company had done anything wrong, saying that publishing proof of concept code for security vulnerabilities is part of his company's job.

"We develop proof of concept code for people to test for a vulnerability, not to give an attacker control of a (computer)," said Max Caceres, director of product management at Core Security.

He said there are many ways that exploit writers could develop code to trigger a vulnerability and he is not sure that his company's proof of concept played any role in the release of the PNG exploit.

"As soon as any vendor releases a patch to the world, it's a clear map to a vulnerability," he said.

Toulouse said that proof of concept code helps exploit writers and malicious hackers more than innocent customers.

"In my thinking, (proof of concept code) benefits attackers more than anyone else. ... We try to give enough information to allow customers to assess the threat to their network, without crossing the line into giving details that attackers can use to leverage that (vulnerability)," he said.

Microsoft will continue to work with third-party security researchers to encourage responsible practices for disclosing security vulnerabilities. The company is also on the lookout for automated attacks, such as worms and viruses, that use some of the recently released exploits, Toulouse said.

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